Instead of creating new threads every time new discoveries are made, just post them here!

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

NASA Completes Webb Telescope Center of Curvature Pre-test[center](Click on the image below for the full article)[/center]

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

Holy Smokes! Color Images of the Schiaparelli [s]Landing[/s] Crash Site![center](Click the image for the full article)[/center][center][/center]

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

It would have if a human was on board! The impact was at over 300 mph I think

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

In the classical theory of general relativity (GR), the event horizon of a black hole is not a particularly interesting place from the point of view of someone who falls in. While an observer far away would see time for them slow down and stop at the horizon due to the gravitational time dilation (and their light would also be redshifted to invisibility), the person falling in does not notice these effects. They find that they fall through the horizon in a finite and quite short amount of time. Similarly, the distant observer may say that all the matter that ever fell into the black hole never actually crossed the horizon, but instead exists in thin shells, like sediment, which approach the horizon asymptotically. Yet the person who falls in never encounters those shells. They pass through the horizon and encounter only empty space there.

This seems like a paradox at first, and might be hard to swallow. But it's really not that weird. You can make sense of it from an analogy to a "sonic hole", where a fluid goes down a drain faster than the speed of sound. Ask yourself what two people would experience if one fell through the drain while talking to another far away. The non-paradox can also be explained with a space-time diagram. And ultimately, it arises from a concept in general relativity called the "equivalence principle", which basically says that no local experiment can determine the difference between freefall in a gravitational field versus freely floating in space far from any mass at all. It means that for the person falling in, the event horizon is not a weird place.

This is all in the realm of classical GR, and observations of black holes thus far (which we do have a lot of) are beautifully consistent with it. However, interesting problems arise when we try to combine general relativity with quantum mechanics. Both are absolutely fantastic theories in their own right (considered among the most successful of all theories in physics), yet it has proven remarkably difficult to unify them into a theory of quantum gravitation. The event horizons of black holes turn out to be one of the places where the contradictions between the two are strongest. It leads to real paradoxes, like the information paradox, which are useful for probing the logic of quantum gravitational theory.

Some proposed resolutions to those paradoxes result in different conclusions. One is the "firewall", which says that the horizon is a weird place which contradicts the equivalence principle. (Personally I was never a big fan of the firewall idea). But whatever the resolution happens to be, it seems that the behavior of real, quantum gravitational black holes might be in some way different than the classical black hole. And this difference might even be observable from a distance.

This paper studies the gravitational wave signals that we have from LIGO thus far, looking for signs of repeated echoes following a black hole merger, after the ring down (where the horizon of the merged black hole settles down into a relaxed shape). Certain characteristics of these echoes can be related to quantum gravitational effects from structure at the event horizon, contrary to the classical GR model of a black hole. The study found a 2.9-sigma confidence in such signals, which is a 1 in 270 chance of being a statistical fluke. This is not enough confidence to make any definitive conclusion, but it does demonstrate the power of the technique.

To be able to perform this kind of analysis so early in this new field of gravitational wave astronomy is very encouraging, and it means that with more detections of black hole mergers, we may expect to convincingly show whether or not we are seeing departures from classical GR. And if we do find them, that will be very exciting.

John Glenn Passed Away Today (8 December, 2016)Click the image for more info

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

Oh, an in-spiraling binary (actually already a contact binary). Yeah, that makes sense. Otherwise I was going to say there is no way we can predict a collision between two separate stars. First it's very improbable for stars to collide in the first place, due to their small sizes compared to the distances between them. Then to actually say with confidence that they would collide, we would need to be able to measure their positions and velocities with extremely high precision. And we simply can't do that -- the uncertainties would be vastly too big. (We can precisely measure their position on the sky, but not their distance, and we can precisely measure how fast they are moving towards or away from us, but not their sideways or "proper" motion.)

So, with a binary, we can predict their merging based on how their orbital periods are changing. If the period is getting smaller, or the orbital velocity getting faster, then they must be getting closer together according to Kepler's Third Law. The telegraph article made an oops and said the orbital speed was decreasing instead of increasing.

Anyway, yeah, this looks pretty credible. I see it's also in Sky&Telescope, and links to the journal articles are below.

gonna be very cool even if its only be bright as polaris and not big nova like SN 1006.i can see polaris from pollution areas so it gonna be like watching the birth of new star in the sky, like a new bright dot for the ppl who dont know about SN 1006 nova:it was probably the brightest astronomical phenomena that ever watched by ppl in the recorded history. it had magnitude of about -7.5see how much bright venus is, and now multiple it by 16!!! that how bright it was. you could watch it even in day time, it was like second sun/moon in the sky

"man cannot discover new oceans unless he has the courage to lose sight of the shore"-Andre Gide

It's a bold prediction, which is fine as long as they are prepared to be proven wrong. The cool thing is that this is something that amateur astronomers can keep an eye on over the next year and possibly collect a lot of useful data.